I have a DBM bottom metal set from Seekins Precision for a Rem 700 in 338 Lapua. This will also accommodate the wildcats based off the Lapua and Rem Ultra Mag casing as well, including the Allen Magnums, Allen Express, 338 edge, etc. I purchased this with the intent of making my rifle a repeater, but have since started a new build in another caliber.
This is NIB, with all necessary parts still sealed in the original plastic as it came from the manufacturer. The set includes the bottom metal, 5 round Lapua extended magazine (latest version), two aluminum posts and 2 torque screws, and complete set of step-by-step instructions.
Note: the installation is not a drop-in, but can be done relatively easily by someone who knows how to work with their hands. The Seekins bottom metal is slightly over-sized, so some minor in-letting is required. Secondly, the bolt stop needs to be moved back just a tad to allow the bolt to pick up the round at the back of the magazine.
These units retail new for $339, plus another $10 for s & h bringing the total to just under $350. I know I will probably have to take a loss on this NIB Seekins DBM, so how about $320 to your door?